In Acrobat X this function will create a new pane in the Tools Panel called "Plug-in Add-on Tools" if it's not already present, and post the button there rather than on the system toolbar or Quick Tools area; but the internal name of the resulting button used by the registry preferences will have the prefix "_legacy:". In this example, if you create a button using the above script and are referring to the button in the Acrobat X registry keys to pre-populate the button into the Quick Tools area, you should use the name

_legacy:myToolButton

However the button itself still has the internal name "myToolButton", so if you try to create it a second time, the script will fail because the name "myToolButton" is no longer unique. Don't use the "_legacy:" prefix in your button-creation script.

Note that in Acrobat X 10.0 you cannot use the app.removeToolButton() method to remove any buttons from anywhere (the toolbars or the Panes), nor can you use the app.listToolbarButtons() function to return an array of all the objects; as the API has no direct connection to the toolbars or Panes. When a script tries to create a new button the Acrobat X API diverts the function call to the Tools Pane, but it's strictly a one-way conversation.